1. Field of the Invention
This invention relates to a process for the gasification of organic materials. More particularly, the invention relates to a process for minimizing scaling and the treatment and recovery of dissolved minerals from the aqueous effluent in a gasification process with minimal discharge of waste products.
2. Description of the Prior Art
High pressure, high temperature gasification systems have been used to partially oxidize hydrocarbonaceous fuels such as coal or organic waste materials including plastic wastes, petroleum coke or sewage to recover useful by-products or energy. The fuels can be admixed with water to form an aqueous feedstock that is fed to the reaction zone of a partial oxidation gasifier. Water is used to quench the hot gaseous products, referred to as "synthesis gas" or "syngas." Water is also used to scrub particulate matter from the syngas and to cool and/or convey particulate waste solids, such as ash and/or slag out of the gasifier.
Davy, "Latest Advances in Zero Liquid Discharge Treatment for Coal Gasification Plants," (Power-Gen Americas Int'l. Conf., Orlando, Fla., December 1994) discloses wastewater treatment options and salt recovery, including the use of falling film evaporator and forced circulation crystallizers.
Coste, "Effluent System in View of Both Zero Discharge and Hazardous Solid Waste Minimization" (undated) discloses a waste water treatment process, including a multiple effect evaporation and crystallization treatment to remove soluble salts.
DeJong, "Coal Gasification and Water Treatment" (pages 90-93) (Synthese Vamn Verworvenheden, undated) discloses wastewater treatment including crystallization of dissolved salts.